Apparatus and Method for Reusing Existing Constellation for Superposed Transmission

1. A method, comprising: deciding, by an apparatus, to multiplex data of at least two users within a super-constellation; determining a power split ratio among the at least two users; selecting a super-constellation; and based on the determined power split ratio, choosing a subset of super-constellation points forming a superposition of modulation constellations of the at least two users, the method further comprising: normalizing a multiplexed signal to nominal power.

2. The method according to claim 1 , wherein the sum of orders of the modulation constellations of the at least two users is lower than the modulation order of the selected super-constellation.

3. The method according to claim 1 , further comprising mapping data bits of the at least two users to the super-constellation points of the chosen subset.

4. The method according to claim 3 , wherein the data bits of at least one of the at least two users are Gray labeled so that each pair of mapped neighbor points differ by a single bit.

5. The method according to claim 1 , further comprising indicating the chosen subset of the selected super-constellation to the at least two users.

6. The method according to claim 1 , wherein the super-constellation is a uniform constellation.

7. An apparatus, comprising: at least one processor; and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to: decide to multiplex data of at least two users within a super-constellation; determine a power split ratio among the at least two users; select a super-constellation; and based on the determined power split ratio, choose a subset of super-constellation points forming a superposition of modulation constellations of the at least two users, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus further to: normalize a multiplexed signal to nominal power.

8. The apparatus according to claim 7 , wherein the sum of orders of the modulation constellations of the at least two users is lower than the modulation order of the selected super-constellation.

9. The apparatus according to claim 7 , wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus further to map data bits of the at least two users to the super-constellation points of the chosen subset.

10. The apparatus according to claim 9 , wherein the data bits of at least one of the at least two users are Gray labeled so that each pair of mapped neighbor points differ by a single bit.

11. The apparatus according to claim 7 , wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus further to indicate the chosen subset of the selected super-constellation to the at least two users.

12. The apparatus according to claim 7 , wherein the super-constellation is a uniform constellation.

13. A computer program product comprising a non-transitory computer-readable medium bearing computer program code embodied therein for use with a computer, the computer program code comprising: code for deciding to multiplex data of at least two users within a super-constellation; code for determining a power split ratio among the at least two users; code for selecting a super-constellation; and code for choosing a subset of super-constellation points forming a superposition of modulation constellations of the at least two users, based on the determined power split ratio, the computer program code further comprising: code for normalizing a multiplexed signal to nominal power.

14. The computer program product according to claim 13 , wherein the sum of orders of the modulation constellations of the at least two users is lower than the modulation order of the selected super-constellation.

15. The computer program product according to claim 13 , wherein the computer program code further comprising code for mapping data bits of the at least two users to the super-constellation points of the chosen subset.

16. The computer program product according to claim 15 , wherein the data bits of at least one of the at least two users are Gray labeled so that each pair of mapped neighbor points differ by a single bit.

17. The computer program product according to claim 13 , wherein the computer program code further comprising code for indicating the chosen subset of the selected super-constellation to the at least two users.

18. The computer program product according to claim 13 , wherein the super-constellation is a uniform constellation.